Is Soy Safe for Women? Here’s What the Research Says

Elizabeth Enochs|

August 29, 2018

Soy tends to be a major player in most plant-based diets, and some studies have suggested that consuming soy foods, like tofu and soy milk, benefits cardiovascular health, weight loss, and prevention of certain cancers. But conflicting soy studies have confused the issue for most consumers, especially women, leaving us all to ask: Is soy safe?

How Soy Works in Your Body

Soy contains naturally occurring estrogenic compounds called isoflavones, the discovery of which seems to have caused a lot of confusion around how soy affects breast health. Isoflavones are considered phytoestrogens, or plant estrogens, which means that isoflavones can mimic estrogen in the body. Since higher estrogen levels are associated with higher risk of breast cancer, many women fear that consuming plant estrogens will increase their risk of developing breast cancer. But that isn’t how isoflavones typically work.

See, women’s bodies have two estrogen receptors, alpha and beta. If an isoflavone binds to the alpha receptor, it could increase a woman’s risk of breast cancer because the alpha receptor causes breast cells to grow. Binding to beta, on the other hand, creates the opposite effect. As it turns out, isoflavones preferentially bind to the beta receptor.

If Your Thyroid Is Healthy, Soy Is No Problem

When doctors make stuff up. To sell you something. Chaps like this should be barred from practicing. https://t.co/cqqxEaAQt3

In the mid-2000s, research found that soy can interfere with the body’s ability to absorb a synthetic thyroid hormone often used to treat hypothyroidism—but soy doesn’t appear to cause thyroid problems. In fact, soy doesn’t seem to affect a functioning thyroid whatsoever. Hever confirms: “Soy foods do not adversely impact a healthy thyroid. However, if you have a thyroid condition, be aware that soy protein may interfere with some thyroid medications, but dosages may be adjusted accordingly.”

If you have a thyroid condition and want to continue eating soy foods, you also need to make sure your iodine intake is adequate. Hever recommends 150 micrograms per day for adults. Additionally, the Mayo Clinic suggests waiting four hours after taking thyroid medication to consume any products that might contain soy protein.

Daily Soy Consumption Can Be Healthy

If you enjoy soy foods and want to consume them daily, Hever suggests sticking with one to two servings each day. She also recommends avoiding processed soy foods: “With any food, I suggest opting for the whole-food version,” Hever says. “So, for soy, whole options include soybeans (edamame), tofu, tempeh, miso paste, and soy milk.”